Caption: MODEL RELEASED. Umbilical cord blood stem cells. Technician holding blood stem cells harvested from a donated human placenta and umbilical cord. The stem cells are able to develop into any type of blood cell, and can be used to treat a number of diseases, including cancers, genetic diseases and blood disorders. The placenta lines the uterus (womb) during pregnancy, providing the foetus with oxygen and nutrients and removing waste products. The umbilical cord attaches the placenta to the foetus.